Three-dimensional semiconductor mounting has become essential for further higher density, higher capacity, higher speed, and low power consumption. A three-dimensional semiconductor mounting technique is a semiconductor production technique by thinning a semiconductor chip, and connecting the chip to another chip using a through silicon via (TSV) to form a multilayer. In order to realize this technique, a step of grinding a surface without a circuit (also referred to as “back surface”) of a substrate on which a semiconductor circuit is formed to thin the substrate, and forming an electrode including a TSV on the back surface is required.
Conventionally, in a step of grinding the back surface of a silicon substrate, a protective tape is attached to a surface opposite to a surface to be ground to prevent breakage of a wafer during grinding. However, in this tape, an organic resin film is used as a base material. Therefore, the tape has flexibility, but inadequate strength and heat resistance. The tape is not suited to a step of forming a TSV and a step of forming a wiring layer on a back surface.
For this reason, a system has been proposed in which a semiconductor substrate is bonded to a support of silicon, glass, or the like, through an adhesive layer to sufficiently withstand steps of grinding the back surface and forming a TSV and an electrode on the back surface. In this system, the adhesive layer used in bonding the substrate to the support is important. The substrate can be bonded to the support without gaps using the adhesive layer, and the adhesive layer needs durability enough to withstand a latter step. Further, it is necessary that a thin wafer be easily delaminated from the support finally. The adhesive layer is referred herein to as “temporary adhesive layer” since it is finally delaminated.
As known temporary adhesive layer and delaminating method, a technique in which a silicone pressure sensitive adhesive is used for a temporary adhesive layer (PATENT LITERATURE 1), and a technique in which bonding and delaminating is carried out using a heat-melting hydrocarbon-based compound for an adhesive material in a heat molten state (PATENT LITERATURE 2) have been proposed. In the former technique, a substrate is bonded to a support using an addition-curable silicone pressure sensitive adhesive, and during delaminating, the substrate is immersed in a chemical agent which is capable of dissolving or decomposing a silicone resin, and then detached from the support. This technique requires a very long time for delaminating, so that application of this technique to an actual production process is difficult. The latter technique is simple because of control only by heating, but does not have sufficient heat stability at a high temperature higher than 200° C. Therefore, the applicable range is narrow.
Further, a technique in which an adhesive material containing a light-absorbing substance is irradiated with high-intensity light to decompose a temporary adhesive layer, and as a result, a thin wafer is delaminated from a support has been proposed (PATENT LITERATURE 3). This technique requires an expensive apparatus such as a laser, and also suffers from a problem in which a processing time per substrate is extended.